Method of winding coils on closed magnetic cores



Jan. 17, 1961 J. G. EVERHART ET AL METHOD OF' WINDING COILS ON CLOSED MAGNETIC CORES Filed Nov. 16, 1956 lIl lllh

2 Sheets-Sheet 1 Mmmm IN VEN TORS. J'ames G. fver'rt .De ang: Fran/(Z421 .DczL/dson Jan- 17 1961 J. G. EVERHART ETAL 2,968,445

nMETHOD oF WINDING coILs oN cLosED MAGNETIC comas 2 Sheets-Sheet 2 Filed Nov. 16, 1956 INVENTORS. JEzmes C5. Ever/:draf .Den/gf FranZn DczL/ason dttorngyn United States Patent METHOD OF WINDING COILS ON CLOSED MAGNETIC CORES James G. Everhart, Sherman, Tex., and Dennis Franklin Davidson, Zanesville, Ohio, assignors to McGraw- Edison Company, a corporation of Delaware Filed Nov. 16, 1956, Ser. No. 622,686

3 Claims. (Cl. 242-6) This invention relates to electrical induction apparatus and in particular to anl improved method for winding an electric coil on a closed magnetic core of electrical induction apparatus.

The present invention is an improvement over the ymethod of winding coils on magnetic cores disclosed in U.S. Patent 2,305,999 in the name of A. G. Steinmayer et al., entitled Method and Machine for Winding Coils, dated December 22, 1942, and having the same assignee as the present invention. In the Steinmayer et al. patent a method is disclosed for winding a conducting coil on a closed magnetic core of the type where the finished coil cannot be slipped over the core, wherein -a split shell having end ilanges is placed around a portion of the magnetic core and roller means engaging both end flanges and revolubly supporting the shell in spaced relation to the core permit winding a coil on the shell when the shell is rotated. Although electrical transformers constructed by this method are highly satisfactory and commercially successful, this method is not ideal in that it kdoes not make the most eiiicient use of the space within the window of the closed magnetic core. Specitically, the presence of the end flanges within the core window prevents winding the electrical coil the entire height of the core window.

It is an object of the invention to provide a method of winding an electrical coil on a closed magnetic core which utilizes the space within the window in the magnetic core with greater efliciency than the method of the aforementioned patent to Steinmayer et al.

Other objects and advantages of the invention will be apparent from the following description when taken in conjunction with the accompanying drawing wherein:

Fig. 1 is a plan view, partly in section, of a closed on the core in accordance with the method of the magnetic core and apparatus for winding electrical coils on the core in accordance with the method of the invention;

Fig. 2 is a front view of the core and apparatus of Fig. 1 with a portion broken away to show the section along line 2 2 of Fig. l;

' Fig-3 is a sectional view taken on line 3-3 of Fig. 1 and showing the details of the insulating shell and illustrating the step of winding an electrical coil on the shell; and

Fig. 4 is a sectional view taken on line 4.-4 of Fig. 3.

Referring to the drawing, a closed magnetic core `y is clamped rigidly to a main frame 11 by suitable clamping-means 12. The core 10 yillustrated in the drawing is of the wound type constructed by winding magnetic strip material of different widths to form a closed, approximately rectangular structure having a cruciform cross section as rshown in Figs. 2 and 3 and annealed to relieve any deleterious strains introduced in the oriented 'grain structureV during construction.

In accordance with the method of the invention,. a straight portion of the core, preferably a winding leg 13, is encircled by a Vsplit annular member adapted to to 2 tatably support an insulating shell placed over the core, the split annular member preferably being a multi-section split gear 14 formed of two elements 15 and 16 detachably joined by links 18. The links 18 are inset within recesses 19 formed in the elements 1S and 16 and are provided at their opposite ends with apertures through which extend screws 20 threaded into the elementsjlS and -16 to lock them together. The split gear 14 is provided with a cylindrical flange 21 which supports one end of the insulating shell upon which the electrical coil is wound as will hereinafter appear. The gear 14 encircling the winding leg 13 of core 10 is revolubly supported in spaced relation to core 10, preferably by three gear members 22, 23 and 24 which mesh with the A lin spaced relation to winding leg 13. The means for supporting shafts 28, 29 and 30 which carry gears 22,

.23, 24 respectively, do not comprise a part of the present invention and have been` omitted to simplify the drawing and facilitate the understanding of the invention. A.though any one of the gears 22, 23 and 24 may be the driving member, as illustrated the upper gear 22 secured to shaft 28 rotatably drives the split gear 14, and the gears 23 and 24 engaging the lower periphery of split gear 14 are idler gears.

Although in the preferred embodiment it has been illustrated and described that a split gear 14 having a cylindrical ange 21 encircles the winding leg 13 and is rotatably supported out of contact with core 10, it will be appreciated that any annular split member may be used, for example a roller or a pulley disclosed in the aforementioned patent to Steinmayer et al., which can be revolubly supported and driven and which can engage one end of an insulating shell 32 placed around the winding leg 13.

Heretofore it was believed necessary to utilize a pair of flanged gears, or rollers, within the core window in order to wind an electrical coil upon an insulating shell surrounding a winding leg of a closed core. lt has been found that ya shell 32 formed of a few layers of insulating paper has sufficient strength to pull wire under relatively high tension if only one end of the shell 32 is driven and a suitable bearing is provided at the opposite end of the shell 32 to permit it to revolve freely about the core, even when the wire is being pulled onto the end of the insulating shell 32 opposite the split gear 14. This method of winding the coil eliminates one flanged gear from Within the core window during the winding of the electrical coil and permits winding over a considerably greater length of the winding leg 13 than with prior methods. The ability of a shell 32 formed of only a few layers of insulating paper to pull relatively highly tensioned wire onto the free end of the shell without. distorting the shell may be at least glass fabric, or polytetrauoroethylene tape around one end of the winding leg 13 to support the free end of the shell 32 provides an adequate bearing surface for the shell to permit winding the coil while driving the shell 32 at one end only. The wrapping 31 may be continuedl until the diameter thereof is approximately the same as the ange 21 on the gear 14, although a single layer of approximately .020 inch pressboard has been found satisfactory for the method of the invention. A shell.32 of insulating material is then placed around the winding leg 13 of the core 10, preferably by winding a sheet of insulating material, for example paper conventionally used for coil interlayer insulation, of appropriate width so that one end encircles the flange 21 and the opposite end surrounds the bearing 31. It is preferable to put a suitable adhesive such as shellac on the first portion 33 of the insulating material so as. to cement the inner layers together adjacent their starting point and to continue the winding ofthe sheet insulating material until a shell 32 (see Figs. 3 and 4) of the requisitev thickness is built up. The shell 32 is shown as a solidmember in Figs. l and 2 and the layers 34 of which it is preferably comprised are illustrated in the relatively larger views of Figs. 3 and 4. It has been found that a shell constructed of three layers 34 of conventional interlayer insulation paper provides adequate mechanical strength for the winding of the electrical coil. After a suicient thickness of the shell has been built up, the end portion 35 of the outermostlayermay be shellacked so as to adhere to the adjacent layer and prevent unwinding-thereof.

It will bev apparent that the method of the. invention can also be practiced by placing a multi-section split cylindrical insulating shell around -Winding leg 13.`

After the shell 32 is formed, anouter layer 36, also preferably of insulating sheet material, is4 wound directly on the shell 32. This outer layer 36 hasV its: marginal edges folded back and forth to form a thickened marginal portion 37, shown in Fig. 4, approximately equal to the diameter of the wire. The folded over marginal portion 37 provides mechanical support to prevent axial movement of the wire turns under short circuit stresses.

The end 4t) of the wire 41 to be wound intol an electrical coil is then anchored relative to the shell 32. Although the anchoring of the wire end 40 can be directly to the shell 32, preferably it is accomplished by inserting the end 40 of the wire 41 through an aperture 42 in the g'ear 14 andA bending over the wire end 40. The shaft 28 is then driven to rotate the shell 32 and pull the wire 41 around the shell 32 until an inner helical layer 44 of. wire is wound on the shell 32. As discussed hereinbefore, apparently the helical woundy layer 44 of wire enhances the ability of the insulating shell 32 to resist distortion while pulling Wire onto the free end of the shell 32. After the wire 41 has been Wound until it covers substantially the entire length of shell 32, insulation sheet material 45, similar to layer 36 and having the marginal edges thereof folded back and forth to provide thickened marginal portion 46, is placed over the rst helical layer of wire, and the shaft 28 is again rotated to build up a second wire layer 47 starting from the free end of the shell 32 and progressing toward the anged gear 14. In this manner the layers 44 ad 47 of wire are built up until a coil of desired electrical characteristics is obtained. The unitary assembly comprising shell 32 and Wire layers 44 'and 47 increases in mechanical strength with the number of wound layers, and irrespective of the tension, the wire 41 is' wound over the entire length of the shell 32 even though only one end of the shell is rotatably driven.

The particular manner in which the coil is formed and the end leads or intermediate leads are arranged does not constitute a part of the present invention and will not be discussed herein.

After the conducting coil has been completely wound', the locking means 18 are removed and the members 15 4 and 16 withdrawn from the shell 32. In order to facilitate removal of the members and 16, preferably one or more of the shafts 28, 29 and 30 supporting the gears 22, 23 and 24 is movable in a direction radially away from the axis of flanged gear 14' to move the plates 25 and 25' out of interfering relation with the teeth on l flanged gear` 14 and thuspermit withdrawal of theange members 15 and 16 from shell' 32. The nished coil is thus'. left in place on the permanently positioned innerl shell, or sleeve 32.

The transformer core 10 is then' reversed anrl` either the same or other clamping means 12 are employed to clamp the core 10 in place so that another coil (not shown) may be wound on-the other winding leg 48 of the closed core.

The method of the invention permits winding of a considerably larger number of wire turns within the window of the closed core and results in much more etiicient` utilization of the core window space than in the method of the aforementioned patent to Steinmayer et al. While only the winding of an electrical coil on one leg of a closed rectangular core has been illustrated and described, it will be appreciated that the invention is not so limited, that coils can also be wound in accordance,

with the method of the invention on polyphase cores having three parallel winding legs, on shell type cores having a winding leg comprising adjacent sides of two rectangular abutting loops, or on the winding leg of any closed core wherein the nished coil cannot be slipped. over the core, and it is intended in the appended claims to, cover all such alternative embodiments and variations of. the method which fall Within the true spiritvand scope. of the invention.

We claim:

1. The method of winding an electrical coil on a closed magnetic core having a' plurality of straight winding legl portions connected by yoke portions, said method compris.- ing the steps of winding strip material around one straight leg portion to form a bearing surface, placing an insulating shell having a length substantially equal to the dis,- tance between said yoke portions around said straight portion so that one end of said shell is supported on said bearing surface closely adjacent one of said yoke portions, encircling said core with a si-ngle split ange and engaging said ange with the opposite end of said shell, revolubly supportingsaidange closely adjacent the other of said yoke portions, anchoring the end of an electrical wire in fixed relation to said shell, rotating said flange and winding said wire into an electrical coil in at least one helical layer on said shell while rotating said flange, and removing the tlange after the coil has been wound.

2. The method of forming a coil on a closed magnetic core having a plurality of straight winding leg portions connected by yoke portions, comprising the steps of placing an insulating shell having a length substantially equal to the distance between said yoke portions around one leg portion of said core, rotatably supporting said shell at one end thereof so that said one end is closely adjacent one of said yoke portions by winding strip material around said one leg portion adjacent said one yoke portion to form a bearing surface for supporting the -inner periphery at said one end of said shell, rotatably supporting and driving the other end only of said shell while said. one end is closely adjacent said one yoke portion by encirclingV said one leg portion with a single split annular member disposed closely adjacent said other yoke portion and having a cylindrical fiange for supporting said other end and rotatably supporting said member at at least three cir.- cumferentially spaced apart points, rotatably driving said member, anchoring the end of an electrical wire in ired relation to said shell, and winding said wireV in at least one-helical layer on said rotatably driven shell.

3. The method of forming a coil on a closed magnetic core 'having apluralityy of' straight winding leg portions connected by yoke portions, comprising the steps of winding a sheet of insulating material having a width approximately equal to the distance between said yoke portions around one of said leg portions into a multilayer shell surrounding said one leg portion, rotatably supporting one end of said shell so that said one end is closely adjacent one of said yoke portions by winding strip material around said one leg portion adjacent said one yoke portion to form a bearing surface for supporting the inner periphery orf said shell at said one end, rotatably supporting and driving the other end only of said shell while said one end is closely adjacent said one yoke portion by encircling said one leg portion with a single split annular member having a cylindrical ange for supporting said other end and revolubly supporting said annular member closely Aadjacent the other said yoke portion, rotatably driving said annular member to thereby rotate said shell, winding an electrical coil on the rotating shell, and removing said split annular member after said coil has been wound.

References Cited in the lile of this patent UNITED STATES PATENTS 2,334,131 Schultz Nov. 9, 1943 2,414,603 Nelson Jan. 21, 1947 2,452,733 Conklin Nov. 2, 1948 

